1. Field of the Invention
The present invention relates to a method and apparatus for bending a metallic flanged member such as an aluminum alloy flanged hollow extruded material.
2. Description of the Related Art
When trying to bend a channel steel in such a manner that a flange thereof is situated on an inner side of a bending process, the flange buckles and then deforms in a wavy fashion. This causes such drawbacks as the channel steel looks poor, it becomes difficult to bring a member into tight contact with the flange so deforming, and the bending rigidity is largely reduced. Conventionally, in order to cope with these drawbacks, there is made a V-shaped cut in the flange from the edge thereof, and after the channel steel is bent, the V-cut edges are welded together directly or via a V-shaped piece. However, this increases bending processes and hence reduces the productivity, leading to high production costs. Moreover, it reduces the reliability in terms of strength.
Described as an improvement to the aforesaid conventional method in Japanese Patent Unexamined Publication No. SHO 51-123760 is a channel steel bending method comprising the steps of forming holes in the root portion of the flange, and thereafter bending the channel steel along the surface of the flange in such a manner that the flange is situated on an inner side of a bending process.
According to the bending method described in Japanese Unexamined Patent Publication No. SHO 51-123760, since holes are formed in the root portion of the flange, the bending rigidity along the flanged surface of the channel steel is reduced, and when trying to bend the channel over a long range with a large radius of curvature, man-hours are increased to form holes to make it possible to thereby lower the productivity. Moreover, reduction in bending rigidity of the channel steel is inevitable.